Does the statement that a prohibition of something necessitates its invalidity imply the invalidity of the prayer of one who shaves his beard or smokes, and of performing ablution in forbidden clothing or a forbidden place, such as a place containing images of living beings, as well as the invalidity of all other acts of worship like reciting the Quran, remembrance (dhikr), supplication (du'a), and seeking religious knowledge?

The Usuliyyun (jurists specializing in the principles of Islamic jurisprudence) differed on whether a prohibition implies invalidity (fasad). The majority held that it implies invalidity if the prohibition is due to the essence or nature of the prohibited act itself. The Hanbalis, however, maintained that it implies invalidity whether the prohibition is due to the essence of the act or to something external but necessarily linked to it.

The general rule of the Hanbali madhhab (school of thought) is that if a prohibition pertains to the essence of the prohibited act or its condition, then the act is null and void (batil). However, if the prohibition relates to an external matter that is neither connected to the essence of the prohibited act nor its condition, then the act is not rendered void.

Examples: The prohibition of fasting on the two Eid days relates to the essence of the prohibited act. The prohibition of a man wearing silk relates to a condition of prayer. The prohibition of deception (ghish) relates to an external matter concerning the transaction, so the sale is not invalidated by it.

However, scholars made an exception for cases where the prohibition is for the right of a human being that can be rectified, such as 'talaqqi al-rukban' (meeting traders outside the market to buy from them before they reach the market and know the price) and 'najsh' (artificially inflating the price of a commodity without intending to buy it). In these cases, the prohibition does not imply invalidity, because the Lawgiver has established the option (khiyar) therein, which is an indication of their validity.